1. Technical Field
The invention includes embodiments that may relate to a membrane. The invention includes embodiments that may relate to method of making the membrane. The invention includes embodiments that may relate to a composition for use with the membrane.
2. Discussion of Related Art
Membranes with a high porosity, wetability, and chemical resistance may be useful in, for example, liquid size exclusion filtration applications. Polytetrafluoroethylene (PTFE) may be desirable for its chemical resistance, and expanded PTFE (ePTFE) may be desirable for both chemical resistance and porosity. However, due to the hydrophobic property of PTFE, liquid water filtration is problematic and may require treatment.
Hydrophilicity, and consequently biocompatibility, may be imparted to an ePTFE membrane by, for example, impregnation using a tetrafluoroethylene/vinyl alcohol copolymer. Such an approach leverages the chemical affinity of the perfluoropolymer in the coating material to the perfluoropolymer of the ePTFE. However, the affinity may be sufficiently low that hydrophilicity is of an undesirably short duration. A porous fluoropolymeric membrane having continuous pores for one side to the other may be rendered hydrophilic by coating the membrane interior with a mixture of a fluoroaliphatic surfactant and a hydrophilic but water insoluble polyurethane. Such an approach may leverage the chemical affinity between the perfluoropolymers to form a two-layer system.
In another approach, hydrophilicity of PTFE membrane may be produced by irradiation treatment of the PTFE powdered resin. The resin may be processed with a porogen and virgin PTFE powder to render a microporous PTFE membrane.
With reference to the above-disclosed methods, there are commercially available hydrophilic ePTFE membranes used for liquid water filtration. In addition to the problematic production considerations, these membranes may be prewetted by membrane manufacturers and shipped wet to end-users. Such a membrane may dewet (dry). The drying of the membrane may render it ineffective and may present, for example, undesirable shipping considerations. Other undesirable aspects may include economic considerations such as handling, shipping weight, and the like.
It may be desirable to have a membrane with properties that differ from those properties of currently available membranes. It may be desirable to have a membrane produced by a method that differs from those methods currently available.